Cancer, an uncontrolled proliferation of cells, is a multifactorial disease characterized by tumor formation, growth, and in some instances, metastasis. Current cancer therapies include chemotherapy and targeted therapies, which attempt to destroy cancer cells via apoptosis, necrosis, or proliferative inhibition. Deoxyribonucleic acid (DNA) repair pathways are frequently overexpressed in cancer cells, and can be essential to the proliferation of chemotherapy-resistant cancers. Thus, compounds that can attenuate aberrant DNA damage repair pathway signaling could be beneficial to cancer patients. However, such signaling pathways in DNA repair and cancer frequently involve protein-protein interactions as critical regulatory steps, making the traditional enzyme active-site inhibitor-based drug development scheme challenging. Accordingly, there is need for development of methods and compositions that target protein-protein interactions in cancer and DNA repair.